With the incorporation of blood pressure measurement into the routine pediatric physical examination and availability of accurate blood pressure distribution curves from a number of epidemiologic surveys, it has become clear that mild elevations of blood pressure may be more common than previously recognized in children. Thus, the issue of the most appropriate medical approach to children with borderline or mild hypertension has become of greater importance. Because antihypertensive drugs may have significant adverse biochemical and metabolic consequences, there is a need to establish whether antihypertensive intervention is feasible, effective and safe using non-pharmacological strategies. This project will test the hypothesis that a reduction of dietary sodium and/or an increase in the potassium-sodium ratio will decrease the rate of rise in blood pressure during normal maturation in children with high normal blood pressure. Participants will be selected from the 6th, 7th and 8th grades of the Minneapolis and St. Paul Public Schools. After two screenings, all children with a systolic blood pressure of 120 mm Hg or greater will be invited to participate in the study. After a complete physical examination and laboratory evaluation, these children will be randomly assigned to one of three study groups: 1) dietary sodium reduction to 70 meq daily sodium intake; 2) daily potassium supplementation of 1 meg/kg body weight; 3) control group without dietary intervention. Children and parents will have two weekly and four bi-weekly education-demonstration sessions followed by tri-monthly education support sessions for the four year duration of the study. Blood pressure will be measured every three months. Assessment of dietary compliance will be made by food records and urine collections every six months. A pre-test of this protocol was initiated in January, 1984. This group will be followed throughout the present study to provide a constant lead time for the study protocol. The results from this study will: 1) establish the feasibility of maintaining children and adolescents on long-term sodium reduction or potassium supplementation; 2) determine the effect of sodium reduction and potassium supplementation on blood pressure during childhood and adolescent development; 3) develop a data base for long-term evaluation of sodium/potassium intervention and the natural history of blood pressure during the adolescent-adult transition.